1. Field of the Invention
Apparatuses consistent with the present invention relate to a 2-axis driving electromagnetic scanner, and more particularly, to a 2-axis driving electromagnetic scanner in which a mirror is separated from a driving unit and directly driven.
2. Description of the Related Art
Recently, a micro electromagnetic scanner having a microscopic structure manufactured by a micro-electro-mechanical system (MEMS) has been actively researched in various technical fields such as in the fields of image display devices, laser printers, accurate measurement systems, accurate fabrication systems, and the like.
A 2-axis driving electromagnetic scanner, which is driven by an electromagnetic force that is exerted by a coil in a magnetic field, horizontally and vertically scans incident light on a predetermined screen area by vibrating a mirror surface with respect to different oscillation axes. For example, a change in a horizontal scanning angle of the 2-axis driving electromagnetic scanner is represented as a high-frequency sinusoidal function. On the other hand, a change in a vertical scanning angle of the 2-axis driving electromagnetic scanner is represented as a low-frequency sawtooth function. Specifically, in order to project an image by using the 2-axis driving electromagnetic scanner, the mirror may be non-resonantly driven according to a sawtooth waveform at a frequency of about 60 Hz with respect to a horizontal oscillation axis and resonantly driven according to a sine wave at a frequency of about 20 kHz, that is a relatively high frequency, with respect to a vertical oscillation axis.
Various techniques for embodying the 2-axis driving electromagnetic scanner have been suggested. For example, a first coil is formed in the mirror, and a second coil is formed in a frame for supporting the mirror. Then, a sine wave at a frequency of 20 kHz, which is a horizontal signal, and a sawtooth wave at a frequency of 60 Hz, which is a vertical signal, are independently applied respectively to the first and second coils. However, in this case, since the first coil is directly formed in the mirror, the mirror is deformed due to a difference between thermal expansion coefficients of the coil and the mirror.
In another example, only a single coil is formed in a frame for supporting a mirror, and a composite signal obtained by combining a sine wave at a frequency of 20 kHz, which is a horizontal scanning signal, and a sawtooth wave at a frequency of 60 Hz, which is a vertical scanning signal, is applied to the coil. In this example, since the vertical driving force and the horizontal driving force are applied to the frame, the mirror is indirectly driven by the horizontal driving force acting on the frame. However, in this example, there is a problem in that there is minute horizontal vibration (horizontal noise) at a frequency of 20 kHz in the vertically driven frame. There is also a limitation in terms of embodying a scanner with high resolution due to horizontal noise. Furthermore, in the case of a resonant driving method in the horizontal direction, since the resonant driving method is an indirect driving method using the driving force of the frame, power consumption increases.
In another example, a coil for a horizontal scan signal and a coil for a vertical scan signal are alternately formed in the frame for supporting the mirror. However, in this example, since the vertical driving force and the horizontal driving force are applied to the frame, the mirror is indirectly driven by the horizontal driving force acting on the frame. Accordingly, horizontal noise occurs in the frame. In addition, since the coils are alternately used, the amount of current needed to drive the mirror is large. Accordingly, power consumption significantly increases.